Boring bar adjustment

ABSTRACT

A boring bar having a nose adjustment screw modified to include different pitch threads and travel nut provided on the abutment end of the screw so that the adjustment obtained is a differential and lesser amount than either would provide separately.

United States Patent Robinson 1 Jan. W, 1972 [54] BORING BAR ADJUSTMENT3,33,13; Ilz lilewski et a1 ..408l156 v 3, ,7 orter ..408/l53 [72]Inventor: James J. Robinson, Southficld, Mich.

7 A Th v I C ti Primary Examiner-Gerald A. Dost 3] sslgnee e aeron Mp0on Attorney-Farley, Forster and Farley [22] Filed: May 18, 1970 211Appl. No.: 38,392 [57] ABSTRACT A boring bar having a nose adjustmentscrew modified to include different pitch threads and travel nutprovided on the (3| ..408/ abutmem end of the screw 50 am the adjustmentobtained is a differential and lesser amount than either would provide[58] Field of Search ..408/146, 147, 153, 181, 185 Separately 1 1Relerwm Cit"! 7 Claims, 4 Drawing Figures UNITED STATES PATENTS2,661,218 12/1953 Snow et a1. ..-.....408/181 Q l I J? T U TFl "I 20 r FI 1 |LLU JO 1 I 1 PATENTEUJANWBY? 3.635.572

i-maa mid/8 I p l/ aaaunium INVENTOR #0145 J FOB/N60 flz mvrug ATTORNEYSBORING BAR ADJUSTMENT BACKGROUND OF THE INVENTION Boring bars withinterchangeable noses that use throwaway inserts are commonly known andused today.

Most of these bars have a guide slot in one part and a matchingprojection or tongue provided on the other which interfit to allow closefitted and guided lateral movement between the two. This enables thenose part, with the cutting insert, to be offset radially and for thetool to provide a reasonable range of bore sizes.

Lateral adjustment is usually obtained by an adjustment screw that is inthreaded engagement with one of the two parts and bears against theother and, since the pitch of the screw threads determines the degree ofcontrol that one has over the adjustment, fine pitch threads arenormally used. However, for precision work the extent of change neededmay require such a slight fractional turn of the screw that is hard toobtain even with fine pitch threads.

At present, only precision adjustment noses, with vemier micrometercutter cartridges or nibs that adjust axially, at an angle, and have thelateral adjustment means as well provide required close toleranceadjustment.

SUMMARY OF THE INVENTION This invention relates to an improvement inboring bars with adjustable noses and, in particular, to a means andmethod for obtaining close adjustment control in such tools, at arelatively low cost.

In boring bars of the type shownand disclosed by U.S. Pat. No. 3,433,104issued Mar. [8, I969, the adjustment screw is threaded in the dovetailprojection of the nose and bears against a stop provided on the bar andreceived in a recess provided for it in one end of the dovetailprojection. The present invention adds a threaded nut on the end of theadjustment screw, between it and the stop, fits the nut to the stop pinrecess so that it acts as a travel nut. Then, a smaller thread pitch isused for the travel nut than for the main body of the adjustment screwso that pitch difference between the two is the extent of movement thatwill be obtained.

This enables much closer adjustment control since a full revolution ofthe adjustment screw, while advancing one thread in the nose part, alsoadvances one thread in the nut thereby, providing an adjustment movementlimited to the pitch differential of the respective threads.

The means and method proposed are readily incorporated requiring only anew adjustment screw, with the different pitch threads on its end, and anut shaped to fit in the stop pin recess.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of a boring bar with alaterally adjustable nose, shown without the cutting insert.

FIG. 2 is another side view, turned 90, showing the dovetail connectionon the nose and bar parts.

FIG; 3 is a cross-sectional view taken in the plane of line 3- 3 in thesecond drawing figure, and shows the adjustment features of the presentinvention.

FIG. 4 is a cross-sectional view taken in the plane of line 4- 4 in thefirst drawing figure and shows a top plan view of the adjustment screw.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT The boring bar shown in thedrawing includes a shank 12 with an enlarged end 14 on which is mountedthe cutting tool nose 16. The bar end 14 is formed to include ways 18,in the form of dovetail slot 20, with outwardly convergingside walls 22and 24 which mate with a'complementary dovetail projection or tongue 26provided on the underside of the nose 16.

The dovetail slot connection enables the cutting tool nose I to belaterally adjusted on the boring bar to obtain a range of cuttingdiameters for the tool.

The enlarged end of the bar is slit, as at 28, lengthwise down thedovetail slot 20, and has two bolt fasteners 30 countersunk in the bodyand extending across the opening for threaded engagement on the oppositeside to close the dovetail ways l8 and clamp cutting tool nose I6 in anyselected position.

FIGS. 2 and 4 show a stop arrangement which is used to limit travel ofthe nose on the bar. It includes, a threaded pin 32, with a socket head,which is provided in the cutting tool nose 16 and can be turned down sothat it extends into an elongated slot 34 in the top wall of one of thedovetail ways 18. Such limit stop slots 34 are provided in both ways toaccommodate either right or left hand cutting tool noses.

In passing, it will be noted that the cutting tool nose 16 is shown witha chip recess 36, within which a cutting insert is to be provided, andthere are also a couple of tapped holes 38, as for the insert clamp.However, no actual cutting insert is shown since its particularlocation, shape and geometry have no critical significance in thepresent invention.

Referring more closely to the dovetail connection, there is an aperture40 extending lengthwise through a control portion of the dovetail tongue26 and which is threaded internally, as at 42, and countersunk as at 44,to receive an adjustment screw 46 therewithin. The screw includes asmaller diameter end 48 that has screw threads of a smaller pitch thanthose at 42, in the nose part, and it has a travel nut 50 fitted to it.

The travel nut 50, on the end of the adjustment screw, is formed to fita recess 52 provided between the threaded end of aperture 40 a reactionshoulder 54 extending from the boring bar end 14, and is restrained fromrotation while free to move axially within the recess 52.

In the absence of the travel nut 50, the adjustment screw 46 itselfcould act against the shoulder 54 to push the cutting tool nose awayfrom it, but the recess 52, in this instance, is made deeper to alsoaccommodate the travel nut 50 on the end of the adjustment screw.

In the embodiment shown, a 24 UNIF thread is provided on the main partof the adjustment screw 46 and a 28 UNIF thread is provided on itssmaller end. When the screw is turned one revolution it will move onetwenty-fourth of an inch through the cutting tool nose in which it isthreaded. At the same time, it will move one twenty-eighth of an inch inthe travel nut 50; which actually means that the nut will be retractedon it (in an outward adjustment situation) that amount. This means thatthe movement obtained, due to the travel nuts engagement with theabutment shoulder, rather than the end of the adjustment screw itself,is the difference between the two or one one hundred and sixty-eighth ofan inch or approximately six thousandths.

The full benefits of the present invention may be obtained by simplycutting the recess 52 deeper, nethreading the end of the adjustmentscrew 46, (or providing a new one) and adding the travel nut 50. For avery nominal cost, a boring bar can be converted from one that providesmerely a range of bore sizes to one which also enables precisionadjustments for close tolerance work.

While only a limited fine adjustment travel through the differentialaction is accommodated by the clearances provided, an initial greatercoarse adjustment may be made in the position of the screw thread 46within the aperture threads 42 before the nut 50 is initially engaged.It will be understood that all fine adjustments are made in a radiallyoutward direction through impressive engagement between the nut 50 andstop 54 lclaim:

1. In a boring bar having a cutting tool nose adjustable thereon bymeans of an adjustment screw acting against a stop, the improvementcomprising;

ditTerential threads provided on the adjustment screw and a rotationallyrestrained travel nut engaged on the end of the screw for engagementwith the stop.

2. The boring bar of claim I,

said screw having threaded engagement within the cutting tool nose andthe stop being provided on the bar.

3. The boring bar of claim 1,

said bar and nose including a dovetail connection therebetween with thedovetail projection being on the cutting tool nose and having said screwextending longitudinally therethrough.

4. The boring bar of claim 3,

the dovetail projection including a recess at one end for the stop, andthe travel nut being fitted within such recess to preclude turning ofthe nut itself.

5. The boring bar of claim 4,

the adjustment screw being provided within a bore hole through thedovetail projection on the cutting tool nose that is threaded toreceivethe screw at its inner end and is recessed within the other end thereofto allow reasonable travel for fine adjustment purposes.

6. The boring bar of claim 5,

said adjustment screw being capable of coarse adjustment beforedifferentially engaging said nut for fine adjustment.

7. The boring tool of claim 1,

said cutting tool nose including a dovetail projection having saidadjustment screw received in threaded engagement therewithin andextended longitudinally therethrough,

said bar including dovetail ways receptive of the dovetail projection onsaid nose and having a limit stop provided at one end thereof forengagement by the adjustment screw,

said dovetail projection including a recess for said stop in one endthereof and of a depth sufficient to also accommodate said nut,

said screw having smaller pitch threads on the end having said travelnut engaged thereto, and said travel nut being formed to fit the recessin the dovetail projection provided for said stop and to precludeturning thereof in the turning of the screw to obtain fine differentialadjustment.

1. In a boring bar having a cutting tool nose adjustable thereon bymeans of an adjustment screw acting against a stop, the improvementcomprising; differential threads provided on the adjustment screw and arotationally restrained travel nut engaged on the end of the screw forengagement with the stop.
 2. The boring bar of claim 1, said screwhaving threaded engagement within the cutting tool nose and the stopbeing provided on the bar.
 3. The boring bar of claim 1, said bar andnose including a dovetail connection therebetween with the dovetailprojection being on the cutting tool nose and having said screwextending longitudinally therethrough.
 4. The boring bar of claim 3, thedovetail projection including a recess at one end for the stop, and thetravel nut being fitted within such recess to preclude turning of thenut itself.
 5. The boring bar of claim 4, the adjustment screw beingprovided within a bore hole through the dovetail projection on thecutting tool nose that is threaded to receive the screw at its inner endand is recessed within the other end thereof to allow reasonable travelfor fine adjustment purposes.
 6. The boring bar of claim 5, saidadjustment screw being capable of coarse adjustment beforedifferentially engaging said nut for fine adjustment.
 7. The boring toolof claim 1, said cutting tool nose including a dovetail projectionhaving said adjustment screw received in threaded engagement therewithinand extended longitudinally therethrough, said bar including dovetailways receptive of the dovetail projection on said nose and having alimit stop provided at one end thereof for engagement by the adjustmentscrew, said dovetail projection including a recess for said stop in oneend thereof and of a depth sufficient to also accommodate said nut, saidscrew having smaller pitch threads on the end having said travel nutengaged thereto, and said travel nut being formed to fit the recess inthe dovetail projection provided for said stop and to preclude turningthereof in the turning of the screw to obtain fine differentialadjustment.